This is super annoying! I only reinstalled the game just before the latest expansion and I can assure you that this is still happening.
One of the reasons I liked having roommates was for the group conversations at home but sadly that seems to be a thing of the past. No sooner has my Sim begun to regale his listeners with some fasinating story but half will have wandered off to look at a plant or something. I've even had my Sim left talking to thin air...😞
It's even more disheartening when they walk off to talk to another Sim.....during a date...😭 This of course could be explained by my Sim being constantly on their phone the rest of the time 😬